1. Field of the Invention
The present invention relates to a pumping light source unit for Raman amplification used as a light source for supplying pumping light in a Raman amplifier, a Raman amplifier using the same, and an optical transmission system.
2. Related Background Art
An optical fiber amplifier is an optical component for amplifying the power of signal light propagating through an optical fiber transmission line constituting an optical transmission system so as to compensate for the transmission loss occurring in the optical fiber transmission line. The optical fiber amplifier placed on the optical fiber transmission line comprises an optical fiber for optical amplification also functioning as a part of the optical fiber transmission line, and a pumping light source for supplying the optical fiber for optical amplification with pumping light. When signal light is fed into the optical fiber for optical amplification supplied with the pumping light, the signal light is amplified in the optical fiber for optical amplification.
As such an optical fiber amplifier, rare-earth-doped fiber amplifiers doped with rare earth elements such as Er (erbium) and Raman amplifiers utilizing Raman amplification phenomenon caused by stimulated Raman scattering are utilized.
Here, a rare-earth-doped fiber amplifier (e.g., EDFA: Erbium-Doped Fiber Amplifier) utilizes an optical fiber doped with a rare earth element as an optical fiber for optical amplification. On the other hand, a Raman amplifier utilizes a silica type optical fiber constituting an optical fiber transmission line as an optical fiber for Raman amplification.